The overall objective of this project is to build and test a model of urban growth which accounts for the impact of social class interaction upon the spatial parameters of a metropolitan area and the reciprocal impact of spatial parameters upon social class. This model goes beyond a simple rich/poor dichotomy to explain the crucial role of the middle class and the social mobility process in affecting the shape of the metropolitan area over time. The principal hypothesis is that while a great deal of occupational, residential and educational mobility can be observed within a metropolitan population over time, these by themselves do not constitute social mobility. Social mobility is here defined as the change in the amount of economic and political leverage which an individual is capable of exerting in society. Thus, residential movement to a more suburban area may not be social mobility if the neighborhood deteriorates relative to others; increased education between generations may not be social mobility if average educational levels advance more rapidly; and occupational movement from blue collar to white collar jobs may prove illusory as social mobility if the status of some white collar occupations decline. Our preliminary findings are that when mobility figures are adjusted for such factors mobility proves limited. Social class entrapment accompanies the expansion of metropolitan areas over time causing social and personal frustration.